In general, a fuel cell system has been proposed as a substitution of fossil fuel and differently from a general cell (a second cell), it supplies fuel (hydrogen or hydrocarbon) to an anode and supplies oxygen to a cathode. Thus, the fuel cell system undergoes an electrochemical reaction between hydrogen and oxygen without a combustion reaction (oxidation reaction) of fuel and thereby directly converts an energy difference between before and after a reaction into electric energy.
As shown in FIG. 1, a fuel cell system in accordance with the conventional art comprises: a fuel cell stack 106 that an anode 102 and a cathode 104 are stacked with plural numbers in a state that an electrolyte membrane (not shown) is interposed therebetween in order to generate electric energy by an electrochemical reaction between hydrogen and oxygen are stacked with the plural number; a fuel tank 108 for supplying fuel to the anode 102; and an oxidant supplying unit 110 for supplying oxidant to the cathode 104.
The fuel tank 108 and the anode 102 of the fuel cell stack 106 are connected to each other by a fuel supplying line 112, and a fuel pump 114 for pumping fuel stored in the fuel tank 108 is installed at the fuel supplying line 112.
As oxidant supplied to the cathode 104, oxygen-including air is used. According to this, the oxidant supplying unit 110 comprises: an air compressor 118 for supplying air to the cathode 104 of the fuel cell stack 106; an air filter 120 for filtering air supplied to the fuel cell stack 106; and a humidifier 122 for humidifying air supplied to the fuel cell stack 106.
Processes for generating electric energy by supplying fuel to the conventional fuel cell will be explained as follows.
When the fuel pump 114 is operated by a control signal of a controller (not shown), fuel stored in the fuel tank 108 is pumped thus to be supplied to the anode 102 of the fuel cell stack 106. Also, when the air compressor 118 is operated, air filtered by the air filter 120 passes through the humidifier 122 thus to be humidified and is supplied to the cathode 104 of the fuel cell stack 106.
Once fuel and air are supplied to the fuel cell stack 106, an electrochemical oxidation of hydrogen is performed in the anode 102 and an electrochemical deoxidation of oxygen is performed in the cathode 104 in a state that the electrolyte membrane (not shown) is interposed between the anode 102 and the cathode 104. At this time, electricity is generated due to movement of generated electrons, and is supplied to a load 124.
In the conventional fuel cell system, oxygen-including air is used as an oxidant thus to generate 4 electrons per a unit reaction. Accordingly, a reaction speed is relatively slow in the fuel cell stack thus to lower a performance of the fuel cell.